Saponin fraction from A. anthelmintica has a promising molluscicidal effect against snails for LC50 of 17.6 ppm as well as a strong biocidal activity against the larval stages of S. mansoni (miracidia and cercariae). A high significant decrease (p<0.001) was recorded in infection rate and survival rate during continuous exposure of the plant; being 50±10 and 44.66±5.05 respectively compared with 81±10.1 in control groups respectively. Light microscopic investigation showed that the tested plant is responsible for the increase of snail's amoebocytes that is consider a main component of the internal defense system of the B. alexandrina snails. Electron microscopic examination showed remarkable apoptotic effects, nuclear chromatin condensation, vacuolated cytoplasm and deterioration in the internal organs as endoplasmic reticulum. It is concluded that exposure of B. alexandrina snails to saponin fraction from A. anthelmintica may be used as a promising molluscicidal and biocidal against the S. mansoni parasite.